Microsoft may upgrade Office 2013 as often as four times a year, the company's top Office executive said this week, a massive change from decades of more measured development.

The faster release pace for Office has been repeatedly touted by Microsoft as one of the benefits to customers who switch from the traditional "perpetual" licensing model—where payments are made once for the right to run software forever—to the Office 365 software-by-subscription plans introduced this year.

In January, Kurt DelBene, who heads the Windows group, cited frequent updates when he introduced Office 365 Home Premium. "This is a major leap forward," said DelBene of his plan to transform the company's traditional three-year release cycle.

But while it has trumpeted the faster pace of changes in Office-by-subscription, Microsoft has been mum about the details, including the frequency of those updates and upgrades, and what they will contain.

This week, however, DelBene gave some of the first hints of what Microsoft has in mind.

At a technology conference hosted by Morgan Stanley, DelBene answered a question about release cadence changes. "We already have the mechanisms in place to update the [Office 365] service on a quarterly basis," said DelBene. "With the client subscription...we'll have the ability to do that with client business as well, the desktop version of Office."

"They have serviced the platforms within Office 365, little things here and there, and they'd like to move to a cloud cadence, if you will, [for Office 2013], too," said Wes Miller of Directions on Microsoft, when asked to parse the clues. But he thought it less than a promise, and if that, not immediate. "It's an ambition, more a goal that they're working toward."

Michael Silver, an analyst with Gartner, was more optimistic that Microsoft would actually pick up the pace, and soon. "[DelBene] is certainly intimating more frequent releases, and I'd expect them to do that."

What those updates would contain remained a mystery to the experts, who speculated that if changes do come frequently, by necessity they would be minor, with a feature here, a tweaked tool there.

"I can see them adding little missing links where the cloud is different from what's on premises," said Miller. "And then at some point, we'll start to see them building software to improve the service."

He envisioned the updates as rolling out changes to, say, Word one quarter, perhaps to Excel in another.

Microsoft has not been forthcoming on that front, either, although officials have repeatedly mentioned "new features" without citing examples.

"If we add new features to it, we can just change the images on our servers," said DelBene this week of Office 2013 subscriptions. "We will actually just stream to you the differences...between the image you have today, and the image that we have on our servers."

Microsoft may be keeping a tight lid on plans for fear of promising more than it can, or will, deliver. If so, it learned a lesson from Windows Vista Ultimate, a top-of-the-line consumer version that Microsoft pledged would receive regular updates with exclusive new features. Instead, Microsoft stiffed Ultimate owners and then quietly discarded the concept.

DelBene also trotted out an out-of-favor phrase to describe the Office updates.

"I think it will get us to a point where we have a major-minor cadence, because there are some investments that have to happen that require a great deal of forward investment," DelBene said Tuesday. "When you're structurally changing the underpinnings of Exchange, or SharePoint, or the Office applications, those take a while to develop. And so I think we'll get into the short cycle where we can add more features, but then we'll have a longer cycle where we really have to intensively change underpinnings of the services."

"Major-minor" was once used by Microsoft to describe alternating releases of Windows, but the term has gone unused for years. "They would say that, but then they would say that every release is major," said Silver about Microsoft. "Here, they're implying that some updates will be new features here and there, and others will be more aggressive changes. But with a 20-year-old product that's so mature, I can't think of really aggressive changes that they might make every year."